Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$65.42	11.102%	$72.6829	$72.68	$72.70	$72.70
Purchase #2	$15.53	6.462%	$16.5335	$16.53	$16.55	$16.50
Purchase #3	$31.57	3.321%	$32.6184	$32.62	$32.60	$32.60
Purchase #4	$131.71	9.262%	$143.909	$143.91	$143.90	$143.90
Purchase #5	$218.83	9.137%	$238.8245	$238.82	$238.80	$238.80
Purchase #6	$16.36	13.820%	$18.621	$18.62	$18.60	$18.60
Purchase #7	$5.59	13.759%	$6.3591	$6.36	$6.35	$6.40
7 purchase totals =	$485.01		$529.5484	$529.54	$529.50	$529.50